Community water fluoridation and birth outcomes
File(s)
Published version
Author(s)
Krebs, Benjamin
Simon, LIsa
Schwandt, Hannes
Burn, Samantha
Neidell, Matthew
Type
Journal Article
Abstract
IMPORTANCE Community water fluoridation (CWF) is a widely implemented public health
intervention aimed at preventing dental caries. However, concerns have emerged about potential
unintended birth outcomes of fluoride exposure, particularly birth weight, which is a widely accepted
summary measure of infant health and has been found to be associated with later-life health and
human capital.
OBJECTIVE To evaluate the association between prenatal exposure to CWF and birth outcomes.
DESIGN, SETTING, AND PARTICIPANTS This cohort study was conducted using an event-study
analysis with a difference-in-differences (DID) approach that exploited the staggered rollout of CWF
across US counties from January 1968 to December 1988. The study included birth outcomes from
singleton births obtained from the National Vital Statistics System’s Natality Detail Files. The analysis
compared within-county changes in birth outcomes before and after the introduction of CWF, using
counties that never fluoridated or had not yet fluoridated as the control. Data were analyzed
between February 4 and October 28, 2025.
EXPOSURE County-level CWF.
MAIN OUTCOMES AND MEASURES The primary outcome was change in mean birth weight, and
secondary outcomes were incidence of low birth weight (<2500 g), gestational length (weeks), and
incidence of prematurity (gestational age <37 weeks). Community water fluoridation exposure was
measured as the population-weighted share of county residents served by fluoridated water based
on Centers for Disease Control and Prevention Fluoridation Census data.
RESULTS The study sample included 11 479 922 singleton births (mean [SD] gestational age, 39.5
[0.8] weeks; 51.2% boys; mean [SD] birth weight, 3337.4 [172.8] g; highest mean [SD] maternal age
proportions, 0.36 [0.13] aged 20-24 years and 0.27 [0.12] aged 25-29 years) across 677 counties
(408 CWF treated [60.3%] and 269 [39.7%] never treated) over the 21-year period, aggregated to
the county-month level. No evidence of an association of CWF with birth weight or other birth
outcomes was found (DID estimate, −0.53; 95% CI, −4.75 to 3.70). Event-study estimates showed no
discernible pretreatment trends and no significant changes following CWF adoption, with estimates
small in magnitude across all posttreatment periods, ranging from −8.44 g (95% CI, −20.41 to 3.53 g)
to 7.20 g (95% CI, −5.45 to 19.85 g). Findings were supported by sensitivity analyses incorporating
state-specific time trends, alternative exposure thresholds, and tests for compositional changes
in births.
CONCLUSIONS AND RELEVANCE This cohort study of more than 11 million births found no
association of CWF with adverse birth outcomes. These findings provide reassurance about the
safety of CWF during pregnancy and underscore the value of rigorous causal designs in evaluating
potential adverse effects of public health interventions.
intervention aimed at preventing dental caries. However, concerns have emerged about potential
unintended birth outcomes of fluoride exposure, particularly birth weight, which is a widely accepted
summary measure of infant health and has been found to be associated with later-life health and
human capital.
OBJECTIVE To evaluate the association between prenatal exposure to CWF and birth outcomes.
DESIGN, SETTING, AND PARTICIPANTS This cohort study was conducted using an event-study
analysis with a difference-in-differences (DID) approach that exploited the staggered rollout of CWF
across US counties from January 1968 to December 1988. The study included birth outcomes from
singleton births obtained from the National Vital Statistics System’s Natality Detail Files. The analysis
compared within-county changes in birth outcomes before and after the introduction of CWF, using
counties that never fluoridated or had not yet fluoridated as the control. Data were analyzed
between February 4 and October 28, 2025.
EXPOSURE County-level CWF.
MAIN OUTCOMES AND MEASURES The primary outcome was change in mean birth weight, and
secondary outcomes were incidence of low birth weight (<2500 g), gestational length (weeks), and
incidence of prematurity (gestational age <37 weeks). Community water fluoridation exposure was
measured as the population-weighted share of county residents served by fluoridated water based
on Centers for Disease Control and Prevention Fluoridation Census data.
RESULTS The study sample included 11 479 922 singleton births (mean [SD] gestational age, 39.5
[0.8] weeks; 51.2% boys; mean [SD] birth weight, 3337.4 [172.8] g; highest mean [SD] maternal age
proportions, 0.36 [0.13] aged 20-24 years and 0.27 [0.12] aged 25-29 years) across 677 counties
(408 CWF treated [60.3%] and 269 [39.7%] never treated) over the 21-year period, aggregated to
the county-month level. No evidence of an association of CWF with birth weight or other birth
outcomes was found (DID estimate, −0.53; 95% CI, −4.75 to 3.70). Event-study estimates showed no
discernible pretreatment trends and no significant changes following CWF adoption, with estimates
small in magnitude across all posttreatment periods, ranging from −8.44 g (95% CI, −20.41 to 3.53 g)
to 7.20 g (95% CI, −5.45 to 19.85 g). Findings were supported by sensitivity analyses incorporating
state-specific time trends, alternative exposure thresholds, and tests for compositional changes
in births.
CONCLUSIONS AND RELEVANCE This cohort study of more than 11 million births found no
association of CWF with adverse birth outcomes. These findings provide reassurance about the
safety of CWF during pregnancy and underscore the value of rigorous causal designs in evaluating
potential adverse effects of public health interventions.
Date Issued
2026-01-01
Date Acceptance
2025-11-22
Citation
JAMA Network Open, 2026, 9 (1)
ISSN
2574-3805
Publisher
JAMA Network
Journal / Book Title
JAMA Network Open
Volume
9
Issue
1
Copyright Statement
© 2026 Krebs B et al. JAMA Network Open. This is an open access article distributed under the terms of the CC-BY License.
License URL
Publication Status
Published
Article Number
e2554686
Date Publish Online
2026-01-20